1. Field of the Invention
The present invention relates to thermal transfer receptor sheets and to thermal transfer processes using receptor sheets of the invention. These processes and receptor sheets are particularly useful in enabling thermal transfer images to be applied to diverse geometric shapes and irregular surfaces.
2. Background of the Art
In a graphic arts design or an artistic environment, it is often necessary to create many preliminary, test, or proof images of a single subject before the final image is accepted. Such preliminary images may be produced by many different media techniques including, for example, color chalk on paper, oil on canvas, water color on paper, dyes in photographic film, and digital images in a computer memory. When many copies of such images are needed, they are usually reproduced as ink on paper by a printing press.
Traditionally in the printing process, the colors making up the design or image are separated using photomechanical (analog) means. This separation requires multiple exposures of the original image through select color filters to obtain so called color separations which can be transferred onto printing plates. Those individual color plates are then used sequentially to print respective colors as ink on paper.
The means most often used to produce full color ink on paper images is a reproduction chain that increasingly allows artists, designers or advertising agencies to expand their creativity. Images are often sought which contain custom colors (as in corporate logo colors) or special color combinations to attract attention. Metallic effects such as silver, gold or copper are also being used more frequently. A system of visualizing how such designs might look as ink on paper is often employed. Such systems are called "proofs" or "proves".
Traditionally, two different technologies are used to produce commercial grade, single sheet (analog) prepress proofs from existing hard copy half-tone separation films. One system is based on powder deposition wherein a colored powder (toner) is directed to adhere to a tacky image, and the other system is based on the change in solubility of a layer of colored photomechanical imaging materials after being imagewise exposed to light. With single sheet proofs, the color information in each of four color separations is produced and overlaid in register to produce a full color reproduction.
Increasing emphasis is being placed on electronic imaging where an image (digital) is constructed by means of computers, graphic design, or publishing programs and a TV like color monitor. Because these images only exist as (digital) electronic files, special equipment is used to make a hard copy for file purposes or approval by an authority higher than the image designer.
Several types of color printer devices may be used to output digital images. Copier (printer) devices at present do not deliver color representations sufficiently indicative of the final image as reproduced with ink on paper to be useful as a proofing image.
To achieve acceptance of the interim or final image produced from such digital files, a proofing or "Proving" device is desirable over a computer (copier) printer. In the case of electronic color images that are destined to convey a concept or predict the final printing of a color image, the difficulty in predicting the final image is complicated by the fact that the image produced by these output devices are not physically and integrally on the same substrate that will be used for the final image.
Commercially, images can be printed on various stocks and surfaces from very thin paper made for publication printing exemplified by what is referred to in the industry as "Brownwood" paper, to highly glossed thick paper for magazine covers or commercial high grade laminated papers called "Chromcoat".
Furthermore, in some design instances it is necessary to visualize the appearance of an image as it would appear when used on round containers such as beer cans, a final box package such as those in which cereal or toothpaste is sold, or a closure such as the toothpaste tube itself. For example, in the packaging industry, innovative container designs are used to effect point of sales purchases. In the packaging industry it is often a requirement that candidate packaging be examined in its three-dimensional form before being approved by the advertising or concept group in charge of merchandising.
The individual proofing color images made by analog means can be transferred to other substrates using the information disclosed in (U.S. patent application Ser. No. 07/728,311). The transfer of such images is facilitated by the fact that each color image exists separately on a layer of polymeric material and the integral color images making up the design as a whole is assembled into a sandwich. Such a sandwich can be used in a cut and paste mode to simulate a box or other diverse shape package. Such hand craft manipulations are time consuming and cost ineffective. The final output of such efforts are at best meager substitutes for the real package.
Images created in an electronic file of a computer and generated on a copier or prover such as those using dye (unit transfer) or mass transfer systems or wax crayon type materials to produce color areas are overprinted on each other without the need for separate integral supports. However, these images also require hand manipulation to form a box, bottle shape, or complex three dimensional design.
In an electronic printer or proofer, the image is in the form of a numerical file. Image data can be transferred to a transducer to enable conversion of that image into a thermal pattern through the use of a wire embedded head or a liquid crystal display which serves as a mask, or by other devices that change one form of informational energy to another.
In systems using thermal transfer, a transducer allows the electronic file to be generated by heat in an imagewise manner. A donor sheet of a fully coated tape or sheet panel of a color on a substrate in contact with a imagewise heated transducer and colorant receptor sheet allows color to be transferred imagewise from the donor sheet to a receptor sheet. These devices theoretically could be constructed so that color can be transferred imagewise to the various can diameters, box dimensions and tubes of various shapes. Such a machine, with the versatility desired to allow for full creative expression, while theoretically possible to construct, is uneconomical to make and use in the work areas normally used by artists and designers. These areas include art studios, offices, and image maker environments of restricted size, shape, and design.
Former techniques for providing transfer images by means of traditional graphic arts mechanical means include techniques wherein an adhesive is applied onto the entire surface of the support sheet and graphic design, relying on various mechanisms for adhesive cleavage of the image area. Specifically U.S. Pat. No. 3,987,225 (Reed et al.) and B.R. 959,670 (Mackenzie) disclose articles wherein adhesive sheer is induced at the edges of the design or incorporated to assist indifferential transfer, by incorporation of a solvent or dispersing powder in the adhesive. Others have used the concept of migrating components to advantage. U.S. Pat. No. 4,177,309, (Shadobolt) uses a polar wax to lower the tack adhesive in contact with image areas while simultaneously unaffecting adhesive in contact with image areas. Tordjiman (U.S. Pat. No. 3,741,787) discloses solvent migration as a means of disrupting the bond between the graphic design and the carrier. Bennett et al. (U.S. Pat. No. 4,454,179) discloses the preparation of a dry transfer technique wherein differential tack and transfer characteristics are achieved by photomechanical means. Specifically, graphics are printed onto the surface of a low energy carrier such as polypropylene and subjected to drying and corona treatment. Both graphics and carrier are overcoated with an actinic radiation responsive adhesive. To facilitate differential tackification the adhesive is exposed, using graphics as an exposure mask. The end result is a diminution or detackification of the exposed adhesive. The article is then burnished to a support and the image transferred to said support. U.S. Pat. No. 3,013,917 (Karian et al.) and U.S. Pat. No. 4,111,734 (Rosenfeld) disclose dry transfer articles employing non-differentially tackified adhesives. The articles disclosed are made by printing ink on to a low energy support to form a desired graphic pattern and overcoating the bottom side of the graphic pattern and exposed portions of the carrier with an adhesive. Application to a new substrate is provided by contacting the article to the substrate and applying pressure. U.S. Pat. No. 4,999,076 (Incromona et al.) describe a transfer system whereby 1) a release liner is coated with at least one layer of adhesive, 2) application in imagewise fashion of at least one layer of an imaging material to the exposed substrate and forming a graphic pattern from the imaging material and adhesive, and forming a graphic pattern from the imaging material and adhesive, 3) contacting the graphic pattern and exposed surface of the adhesive with a carrier film having high compatibility with the adhesive and low compatibility with the graphic pattern and 4) applying sufficient pressure, and if necessary heat, to the carrier film to adhere the adhesive there to. This disclosure makes a special point of stressing that the imaging material be applied to the adhesive and that the graphic pattern be subsequently formed thereof (by drying, curing, fusing, etc.). Prime coats for the described construction include Boehmite, modified silica, etc.
The use of dye sublimation as a transfer medium is not new, having been described in U.S. Pat. No. 4,088,442, U.S. Pat. No. 4,076,495, and U.S. Pat. No. 4,008,998 which describe dye image transfer by dye sublimation from intermediate 3-4 color sublimable images printed onto a carrier sheet. Transfer of images produced by the exposure of sequentially coated panels of sublimable color panels and their retransfer onto diverse final supports are described in "Color in Color" by Dybvig, Revensen, Ulseth, and Wiese in "Color Theory and Imaging Systems" edited by R. Enyard, Published by the Society of Photographic Scientists and Engineers, 1962 pages 403-411. Image transfer from an intermediate sheet to a final substrate after initial image-wise sublimation is also described in this paper. Heat retransfer of sublimable color images made by analog dye transfer means is also described in U.S. Pat. No. 4,006,018. Additional art illustrating the use of volatile dyes of the type used in dye transfer printing can be found in U.S. Pat. No. 3,767,394 wherein an analog process is employed to transfer coated sublimable dyes by infra-red absorbing images. U.S. Pat. No. 4,251,611 teaches the transfer of a dye sublimation image formed by digital laser exposure of a photoconductor and dye attraction by electrostatic means to said photoconductor. The image is transferred to a support and then retransferred to a final support.
In areas of prepress proofing transfer systems including those wherein a photosensitive layer is made to coat over a low adhesion material and, after being imaged and processed to disclose a visible image, the formed image areas are made to transfer to a substrate either as an individual colored image or as a packet of at least 4 different color images each formed by the process of exposure then development, then transferred individually until a full 3-4 color image is completed, such a transferred pattern consists only of images that are isolated from one another (individual halftone dot areas) without the benefit of interstitial binder or a joining adhesive layer. Other systems have image areas formed by exposure of a photosensitive color containing or color adjacent layer laminated onto a temporary receptor which is developed and then reapplied to a second support as a single sheet containing a packet of individual color images. In this type of system, a full image (that is an image consisting of a series of layers of different color dots) without interstitial binder is transferred in situ with an adhesive layer holding the halftone dots (Matchprint.TM.). Under certain circumstances the first transferred layer can again be transferred (2nd transfer) to a final support.
More recently, thermal-transfer type color provers or printers have been developed using either dye transfer or mass transfer (single or first transfer) from color containing donor sheets to a final support, such final supports being a specially prepared final sheeting. Although a more market acceptable rough paper is needed, transfer systems today have difficulty in making a first transfer to this type surface. References on these points include S. Masuda, N. Kihara, and O. Majima "Color Video Printer" IEEE Transaction on Consumer Electronics, CE-28 (3) pp. 226 (1982) and N. Taguchi, T. Shimixu, A. Imai, S. Hotta, S. Mina, and H. Irie "Dye Transfer Type Thermal Printing Sheets" Proceedings of the 14th Joint Conference on Image Technology.
Such transfers are from color donor sheet to a first transfer receptor (one-shot or final receptor). To facilitate such transfers (facilitation includes continuous tone not mass transfer of color images, uniform dye coverage of solid layers, reduced friction or smooth transport through the printing device during the transfer action), inventors have resorted to spherical or non-subliminal spacers in either the donor sheet and/or the 1st transfer (receptor) layers (U.S. Pat. No. 4,541,830, 4,772,582, and 4,876,235). Such spacers are placed in the top surface of said layer and protrude through that surface to provide an air interface between donor and receptor.
Also described are coated layers on top of a color donor sheet, such layers containing polysiloxane materials having terminal hydroxyl groups (E.P. 2011969, T. Kawakami, H. Matsuda, S. Tanimore and S. Sano). Other have used donor layers containing silicone or fluorinated moisture cured resins (E.P. 336394, A. Imai, et al.). Receptor sheets containing polyester resin and white micropowder (J.P. 63001595) have also been employed for this purpose. Other patents including U.S. Pat. No. 4,772,582, A. Imai, et al. and Hotta et al. U.S. Pat. No. 4,541,830 described receptor sheets containing uniformly distributed, non-subliminal particles to form surface irregularities to enable stable running, good color depth, and reduced color drop out and noise.
U. S. 4,923,848 assigned to Dai Nippon Printing, Co. claims a process for forming sublimation transfer images on an objective body. The process involves 1) making a 3-4 color sublimation transfer image on a receptor sheet, and 2) retransferring the formed sublimation transfer image to a final surface. This process seems to be capable of retransferring the sublimation transfer image only once, resulting in a mirror image of the original. This process is similar to those disclosed in U.S. Pat. No. 3,906,138 in which a transparent secondary print is formed by the re-transfer of a sublimation dye from a formed image onto a temporary primary sheet.
U.S. Pat. No. 4,923,848 describes the imagewise transfer of dye sublimed images from donor sheet (transfer 1) to a transfer sheet (transfer n). The transfer steps cannot proceed past n+2. The receptor sheet in U.S. Pat. No. 4,923,848 consists of a image receiving layer and a layer of hot melt adhesive adjacent to the support (referred to in this application as an "A" sheet). The imaged "A" sheet is mated coated layer to coated layer to a "B" sheet containing an adhesive layer and a film protective layer. In this invention the "A" sheet consists of a dye receptor layer, an optional barrier layer, and a hot melt adhesive layer to affect image-wise transfer of a dye (transfer 1) to a transfer sheet (n) and from that sheet to many sheets (n+ infinity). In all such transfer actions in this invention, the layer closest to the base of the transfer sheet ("A" sheet) is the top layer on the transferred image (a hot melt adhesive). In such systems the top layer provides the adhesive force to remove the image from its prior support. In U.S. Pat. No. 4,923,848 the unused "B" sheet is described as having a film protective layer closest to its support. Images transferred from an "A" sheet to a "B" sheet (transfer n) result in having a film protective layer on their upper surface. They therefore have no adhesive properties for further transfer (n+1). In this invention both used and unused "B" sheets have an upper layer of hot melt adhesive allowing infinite transfers. Transfer repetition is only limited by the flexability needed in the last transfer/ retransfer step.
Addenda have also been described for coated layers on top of a non-transferable color donor sheet, such layers containing polysiloxane materials having terminal hydroxyl groups (E.P.O. 2011969, T. Kawakami, H. Matsuda, S. Tanimore and S. Sano). Other have used donor layer containing silicone or fluorinated moisture cured resins (E.P.O. 336394, A. Imai, et al.). Receptor sheets containing polyester resin and white micropowder (J.P. 63001595) have also been employed for this purpose. Other patents including U.S. Pat. No. 4,772,582, A. Imai, et al. and Hotta et al. U.S. Pat. No. 4,541,830 described receptor sheets containing uniformly distributed, non-sublimable particles to form surface irregularities to enable stable running, good color depth, and reduced color drop out and noise.
Substrates using waxes have also been described (E.P.O. 319331, N. Taguchi, et al.), as have dye donor sheets with dispersions of colloidal silica in a polyester resin or silane copolymer (J.P. 1034784 [EPO 312637], A. Iami et al.). Dye Transfer materials (donor sheets) have been described using lubricant or heat releasing particles protruding above the level of the sublimed dye coating to improve running stability. Receptor layers (Single Transfer Receptors) have been disclosed containing matrices with silane couplers, and colloidal silica particles (E.P. 261970, H. Matsuda et al.) to improve dye transfer and smooth transfer during printing.
The objective of the present invention is to provide materials and processes that enable the transfer and retransfer of a thermal dye and/or mass images multiple times, allowing both the production of correct-reading images as well as mirror images on a variety of final supports.
Additionally, a color transfer printing machine has been described in "A High Speed Dye Transfer Printing Process Applicable To Rough Paper" by N. Taguchi, A. Imai, and Y. Fukui of Matsushita Electrical in Preprints of Technical Papers presented at the May 1991 meeting of the Society of Imaging Technology in Minnesota pgs. 308 to 311 which allows a double transfer system to improve image transferability. Such a device uses two heated sources. The first is a matrix of imbedded wires to transmit a digital signal to a donor sheet in contact with a first transfer sheet. The transfer is done individual color by color using a thermal print head, with an originating (first) dye transfer sheet transferring color onto an intermediate transfer sheet. The device then allows the individual first transferred color layer to be additionally transferred to a rough paper sheet by means of a nonimaging hot roller. It should be noted that this transfer is accomplished individual color by color until a single full color image (3 or 4 color image) is obtained. It is believed that the material in use in this device is described in J.P. 58220788, N. Taguchi, T. Shimizu, S. Hotta, W. Shimotsuma and S. Arai.